1. Field of the Invention
The present invention relates in general to a thermal management device for use with a battery. In particular the present invention relates a thermoelectric cooling and heating device disposed within the cells of a battery to effectively cool the battery during rapid charging as well as heat the battery during colder periods.
2. Prior Art
There have been numerous attempts and initiatives established for next generation land based vehicles. Some programs have set goals for vehicle mileage of 80 miles/gal and greatly reduced vehicle emissions based on today's standards. Federal and local governments have placed limits on emissions as well as standards for fuel consumption. Even with regenerative braking energy, a hybrid electric/internal combustion vehicle will be pressed to meet these goals.
Hybrid, All-Electric and internal combustion types of vehicles will need a means to store energy on board. For the present, the means of choice is lead-acid batteries, with the hybrid electric vehicle having auxiliary power supplied by a small internal combustion engine. The technology of lead-acid batteries is well known in the art and is therefore the battery of choice based upon economics, availability and reliability.
One of the main drawbacks to lead-acid batteries is internal heat buildup as a natural consequence of the discharge process as well as I.sup.2 R losses during discharge and high rates of charging. This limits the recharging rate to the battery for an electric vehicle which has a limited range of about 80 miles. To become practical a quick turnaround on recharge is needed. One of the factors preventing this advancement is the heat build-up during quick recharge.
In a hybrid electric vehicle application the auxiliary power unit provides a continuous charge to the battery energy storage system. As such, heat generation in the lead-acid battery is a constant problem that must be addressed to reduce thermal damage to the batteries.
There are many patents that disclose various attempts aimed at cooling the battery during charging. U.S. Pat. No. 4,007,315 discloses liquid coolant tubes disposed in the electrolyte above the plates of the battery attempting to remove the heat generated in the battery. U.S. Pat. No. 5,569,552 discloses a double-walled battery in which to circulate liquid in an attempt to cool the battery. U.S. Pat. Nos. 5,623,195 and 5,121,047 disclose charging schemes which attempt to limit or reduce the effect of the thermal build-up in the cells during charging. Although these charging schemes are effective in lowering the thermal build-up in batteries during a charge they disadvantageously prolong the charging cycle.
None of the aforementioned prior art designs are aimed at the heart of the cell of a battery where the thermal energy is produced. What is needed is a thermal management device in batteries that will better manage the heat build-up in the hybrid electric vehicle as well as allowing for a much quicker charge in the all-electric vehicle, reducing the heating problem significantly in the battery energy storage units of these vehicles. It has been estimated that an average operating temperature of 10.degree. C. higher shortens the lifetime of the battery by half. Therefore, it is of paramount importance that the temperature of the battery, and hence the amount of thermal energy that is produced in the battery, be managed accordingly.